Heretofore, several compounds having a vasopressin antagonistic activity have been developed (e.g., Patent Literature 1 to 3 and Non-Patent Literature 1 and 2). However, the development of a compound having more excellent vasopressin antagonistic activity is in demand.
Patent Literature 3 discloses, in Example 430, compounds exhibiting excellent vasopressin antagonistic activity. Of such compounds, tolvaptan, represented by the following formula, is also disclosed.

However, Patent Literature 3 is silent about the deuterated compound of the present invention.